Depilatory paint thickener comprising an anylopectin starch

ABSTRACT

The invention relates to the dehairing (depilating) of animal pelts, hides or skins, more specifically to depilatory paint and depilatory paint (depilation paint) thickener used in the depilation process in for example fellmongeries. The invention provides a depilatory paint thickener comprising a starch containing essentially only amylopectin molecules. Such thickener, is among other things, easily soluble in cold water; improves diffusion of chemicals (like sulfide or lime) throughout the skin; improves viscosity or resistance to shear of a paint, whereby less starch is needed to exert a similar effect; and increases the suspendability of a lime, allowing less time to be used which creates environmental advantages in waste disposal.

This application claims priority based on International Application No.PCT/NL99/00461, filed on Jul. 19, 1999 and EPO Application No. EP98202457.2, filed on Jul. 22, 1998.

BACKGROUND OF THE INVENTION

The invention relates to the dehairing or dewooling (depilating) ofanimal pelts, hides or skins, more specifically to depilatory paint anddepilatory paint (depilation paint) thickener used in the depilationprocess in for example fellmongeries.

Depilation is a process whereby a depilatory paint is applied to a(sometimes pre-shorn) hide or skin and let to soak for several hoursduring which chemicals act to de-hair the skin. During that time, thepaint should remain in place to provide for continuous chemical action,for which a certain thickness or viscosity is required. Afterdepilation, the skins or hides (now often called slats) are washed andcleaned for further processing. Depilated hair is in general not furtheruseful, depilated wool (now often called slipe wool) sometimes findsfurther use.

Traditionally (see depilatory thickeners, S. M. Cooper, New ZealandLeather and Shoe Research Institute) hydrated lime has been used forthickening depilatory paint. It has a number of advantages. It workswell as a thickener because of its low solubility. It provides an alkalireserve for the depilation processes to keep the pH high enough for hairor wool loosening. It is readily available, and best of all it is cheap.Lime is still used for paint thickening in quite a high proportion offellmongeries. However lime does have disadvantages when used as athickener. In general, it does not stay in suspension. Furthermore,pelts painted with a low lime-paint tend to have a brighter grain, andthey require less washing out of lime and are easier to delime. A numberof alternative thickeners have been tried. Among the most successful arepregelatinised potato starch ethers. Pregelatinised potato starch ethersgive good thickening at low concentrations of 1.5 to 3 percent. They arereasonably easy to mix into the paint, at least compared to some of thealternative non-lime thickeners, and they do not require any heating.However, in general they are not as easy to mix as lime. Unlike some ofthe non-lime thickeners, they are not so tacky that they cause stickingproblems, with pelts sticking to each other or the boards of the pullingmachines. They do not tend to have drip problems, and paint thickenedwith these thickeners is stable when sprayed under pressure. With somethickeners thinning under pressure leads drip problems. By using somelime in the system to act as an alkali reserve, sodium hydroxide is notneeded to increase the pH. However there have been some problems inproduction. Paints thickened with these thickeners not always havebehaved completely consistently when sprayed onto pelts, and this hascaused problems of too much or too little paint on the pelts, or unevencoverage. This can lead to difficult pulling or residual wool problemsor in some cases pelt damage.

It is thought that these inconsistencies are due to small changes in theviscosity of the paint from day to day, due to slight changes in theproportion of ingredients or the method of mixing, or even thetemperature during mixing or application of the paint. Small differencesin viscosity could lead to differences in application rate because aspray system is very sensitive to viscosity changes.

The operation of the depilation process can be looked at in two ways;

a) The Processes Taking Place in the Fellmongery

These are the observable processes that are carried out in thefellmongery on the skin and are controlled by the fellmongery manager.The process-steps involved may consist of; Wash; pre-flesh; squeeze orspin dry; apply depilatory paint; hold skins; remove wool.

Each of these processes are controlled to give good clean hair or woolremoval with minimal damage to the skin.

b) The Underlying Processes

This requires an understanding of what is occurring as the depilatorypaint is penetrating the skin, i.e.

how do sulphide and hydroxide penetrate the skin;

how much hydroxide and sulphide bind to the collagen in the coriumlayer;

how the sulphide and hydroxide react with the wool roots; theequilibrium between sulphide and hydrosulphide.

To date, depilation research has looked at the processes carried out onthe skin and their improvement without looking at the underlyingprocesses that are occuring in the skin. Approaching depilation from theview of the underlying processes will enable the critical processes tobe determined. These processes can then be optimised to give betterdepilation performance.

The optimisation and control of these critical processes depend on theability to observe what is occurring, both on the underlying processesand the processes carried out. Factors which are of importance duringdepilation are:

thickness of skin; paint performance; paint application rate; rate ofpenetration of chemicals.

Current techniques for application of depilatory paint involve applyinga larger amount of depilatory paint to the centre of the skin. This isto compensate for the assumed 2:1 ratio between the thick and thinregions of the skin. However the actual ratio between the thick and thinregions of the skin may be much larger than assumed. This may mean thatthe differential spraying technique may not deliver enough paint to thethicker areas of the skin.

If the correct amount of paint at the correct concentration is appliedto the skin, there may still be problems with depilation if the spraypattern does not hold. Common starch thickeners are currently used inthe industry to hold the spray pattern. However, even with the additionof common starch thickeners it is often found that when the skins arestacked or pole hung that the spray pattern will shift. A correctlythickened paint should not produce such paint migration.

To ensure that paint migration does not occur, a depilatory paint mustbe thickened correctly with a suitable thickener. The means ofdetermining the suitability of a thickener for depilatory paints has notalways been well understood. Often the thickener used has relied onsuggestions from chemical companies. The selection of a thickener bythis means may not always meet-the requirements of depilation. Todetermine the suitability of a thickener for a depilatory paint, therequirements of depilatory thickeners must be understood. Theserequirements can be put into four categories:

1) Viscosity Requirements

For a thickener to be considered suitable, the thickener must providethe required level of viscosity consistently and simply. Specialhandling requirements limit the use of the thickener in the fellmongerysituation. To satisfy this the thickener should;

Thicken at normal temperatures (20-25° C.) without requiring heating.

easily disperse without lumping into sulphide solutions without the needfor high speed agitators.

not be sensitive to shear.

2) Stability Requirements

Not only should a depilatory thickener provide the required level ofviscosity, but it should also be stable, ie the thickener should not bebroken down or form solid gels by process or chemical conditions. Thiscan be satisfied if the thickener;

is not thinned excessively by mixing too long.

is stable under high NaOH and sulphide concentrations, e.g. does not gelor thin over time.

provides paints of consistent viscosity, e.g. will make the same paintagain and again.

3) Tack Requirements

When two skins are placed together flesh to flesh after depilatory hasbeen applied, there maybe some adhesion of the skins making pullingapart difficult. To be acceptable as a depilatory paint thickener, thethickener should not adhere skins when skins are placed together fleshto flesh for 2-3 hours.

4) Downstream Processing Requirements

The use of the thickener should not have any adverse effects on anyfurther processing that may be carried out. The thickener;

should not affect the quality of the slats produced.

should not affect the quality of the slipe wool produced.

should not increase the waste treatment loading.

should easily be washed out.

SUMMARY OF THE INVENTION

The invention provides a depilatory paint thickener comprising a starchcontaining essentially only amylopectin molecules. Such a thickener isamong others easily soluble in cold water; improves diffusion ofchemicals (like sulphide or lime) throughout the skin; improvesviscosity or resistance to shear of a paint, whereby less starch isneeded to exert a similar effect; and increases the suspendability of alime, allowing less lime to be used which creates environmentaladvantages in waste disposal.

SUMMARY OF THE INVENTION

Starches, both of the common variety containing both amylose andamylopectin, obtained from both cereals and tubers or roots and of thewaxy variety, containing essentially only amylopectin molecules (e.g.0-5% amylose), obtained from cereals, are widely used in foodstuff.

Common starch consists of two major components, an, in essence, linearα(1-4)D-glucan polymer (branching is found at a low level) and aelaborately branched α(1-4 and 1-6)D-glucan polymer, called amylose andamylopectin, respectively. Amylose has in solution a helicalconformation with a molecular weight in the order of 10⁴-10⁵, or higher.Amylopectin consists of short chains of α-D-anhydroglucopyranose unitsprimarily linked by (1-4) bonds with (1-6) branches and with a molecularweight of up to 10⁷, or higher.

Amylose/amylopectin ratios in native starches in plants are generallyanywhere at 10-40 amylose/90-60% amylopectin, also—depending on thevariety of plant studied. In a number of plant species mutants are knownwhich deviate significantly from the above mentioned percentages. Thesemutants have long been known in maize (corn) and some other cereals.Waxy corn or waxy maize has been studied since the beginning of thiscentury. Therefore, the term waxy starch has often been equated withamylose free starch, despite the fact that such starch was in generalnot known from other starch sources such as potato but mainly derivedfrom corn. However, industrial use of an amylose free starch has neveroccurred in depilation processes in fellmongeries.

In a preferred embodiment of the invention a depilatory paint thickeneris provided wherein said starch containing essentially only amylopectinemolecules has been derived from a genetically modified plant. Amyloseproduction in a plant is among others regulated by the enzymegranule-bound starch synthase (GBSS), which is involved in generatingthe amylose content of starch, and it has been found that many of thewaxy cereal mutants described above lack this enzyme or its activity,thereby causing the exclusive amylopectin character of these apparentlynaturally genetically modified cereal mutants.

An example of a thickener provided by the invention is a starch obtainedfrom an amylose-free potato plant which is for example lacking GBSSactivity or GBSS protein altogether, thereby lacking amylose and havingessentially only amylopectin molecules. In a preferred embodiment of theinvention a depilatory paint thickener is provided wherein said starchfrom is derived from a genetically modified non-cereal plant, forexample from a potato, banana, yam, canna or cassave. Geneticmodification of non-ceraeal plants such as tuber or root plants is askill available to the artisan, and for example involves modification,deletion of or insertion in or (antisense) reversion of (parts of) agene, such as a gene encoding granule-bound starch synthase (GBSS),which is involved in determining the amylose content of starch. In orderto manipulate such crop plants, efficient transformation systems andisolated genes are available, especially of potato, and others are foundby analogy. Traits, such as absence of amylose, that are introduced inone variety of a crop plant can easily be introduced into anothervariety by cross-breeding. In the experimental part of this descriptiona thickener is provided wherein said modified starch is obtained from agenetically modified potato, for example from a genetically modifiedpotato plant variety. Examples of such a potato plant variety are thevariety Apriori, Apropos or Apropect, or varieties derived thereof.

In a further embodiment of the invention a depilatory paint thickener isprovided wherein said starch is a cross-linked starch, such as aepichlorohydrin cross-linked starch.

Crosslinking starch is in itself a method available to the artisan,various cross-linking agents are known, examples are epichlorohydrin,sodium trimetaphosphate, phosphorous oxychloride, chloroacetic acid,adipic anhydride, acrolein, dichloro acetic acid or other reagents withtwo or more anhydride, halogen, halohydrin, epoxide or glycidyl groupsor combinations thereof which all can be used as crosslinking agents.

In a preferred embodiment a depilatory paint thickener is providedhaving a degree of cross-linking varying from 0.001% to 0.5%, preferablyvarying from 0.01% to 0.1%, more preferably varying from 0.025% to0.05%, for example varying on whether the cross-linking occurs insolution or suspension. In the experimental part of this description amuch preferred thickener is provided having a degree of cross-linking ofbetween 0.025% to 0.05%, such as 0.033%, cross-linked in solution.

In yet another embodiment of the invention a depilatory paint thickeneris provided wherein said starch is a stabilised starch, such as ahydroxyalkylated starch. Stabilisation by hydroxyalkylation orcarboxymethylation of starch is for example obtained with reagentscontaining a halogen, halohydrin, epoxide or glycidyl group as reactivesite. Chloro acetic acid (or its salt) is used as carboxymethylationreagent. In one embodiment of the invention said starch is stabilised byhydroxypropylation, hydroxybutylation, hydroxyethylation and/orcarboxymethylation.

In a preferred embodiment of the invention a depilatory paint thickeneris provided comprising a stabilised starch having a molar degree ofsubstitution (MS) varying from 0.01 to 1.6, preferably from 0.1 to 1.2,more preferably from 0.2 to 0.8.

In a further embodiment, the invention provides a depilatory paintthickener wherein said starch is an pregelatinised or cold-water solubleor instant starch, providing easy solubility to a thickener. In generalstarch or starch derivatives are relatively insoluble in cold water.Viscosity and water binding is achieved by heating or cooking. Forconvenience starches are sometimes pre-gelatinised i.e. pre-cooked anddried. These starches are referred to as instant starches and performwithout heating or cooking. Pre-gelatinisation can for example beachieved by spray cooking, spray drying, roll drying, drum drying,extrusion heating in aqueous water-miscible organic solvents or underhigh pressure.

A paint thickener as provided by the invention provides good and stableviscosity and shear resistance to a depilatory paint. Due to its highand stable viscosity and water binding properties, it can in general beused at lower concentrations than a thickener comprising a common starchwith normal contents of amylose. It provides protection against abrasionof skins, especially during the stacking of the skins. It furthermoreenables easier separation of stacked, limed pelts as it prevents dryingout of the paint due to its high water binding properties.

The invention furthermore provides a depilatory paint comprising athickener as provided by the invention. Such a depilatory paint canadvantageously be used in a depilation process. Such a paint providesfaster penetration of the paint chemicals through fat deposits, wherebyit emulsifies the fat. In such a paint, the lime concentration or pH iseasy to adjust, due to the stable viscosity of the product under variousconcentrations of chemicals used. In general, less lime is needed toexert a similar function and sulphide strength is increased.

The invention further more provides a method for depilating an animalhide or skin comprising treating said hide or skin with a depilatorypaint provided with a depilatory paint thickener according to theinvention. Such a method provides easier and effective pulling,contributing to an even and high quality of the produced slats andleather. The risk of abrasion is minimised, thereby reducing the numberof damaged slats or pelts to go into the pickling and chrome tanningprocess, thereby reducing the number of pelts that turn out as damagedwet-blue after tanning.

The invention furthermore provides a depilated hide or skin produced bya method according to the invention and provides leather or a leatherproduct derived thereof. Such hides or skin and leather and leatherproducts are characterised by more even tanning and less abrasions,having a good clear grain and no mottle.

The invention further provides (slipe) wool obtained from a hide or skintreated by a method according to the invention. Such a wool is brighterand softer and less damaged than ordinary slipe wool, and finds betteruse.

The invention is further described in examples, tables and figures inthe experimental part of the description which are not limiting theinvention.

EXAMPLE 1

The main properties required for a thickener of depilatory paints are:

high thickening power in depilatory paints,

stability on ageing,

good reproducibility of the preparations,

good stability to shear,

easy dispersion of the flakes in the depilatory paints, no lump forming.

In example 1 the properties of 3 commercial products, based on potatostarch, commonly used in the depilatory paints (products A, B and C)have been compared with 2 other products also based on potato starch(products O and P) and a product based on amylopectin potato starch(product I).

1Experiments

1.1Measurements of Brookfield Viscosity in Tap Water

Preparation of a solution by:

dispersion under mechanical stirring at 450 rpm (6 holes-blade stirrer)of the starch in tap water in order to have a total weight of 500 g;

stirring at 450 rpm for 30 minutes;

rest for 15 minutes;

measurement of the viscosity at 20° C. with a Brookfield viscometer RVTat 50, 20 and 10 rpm.

Measurements have been done at several concentrations for each productdepending on their level of viscosity. With the products O and P, theaddition of a few drops of an anti-foaming agent is necessary.

1.2Stability to Ageing

The stability to ageing has been evaluated by measuring the Brookfieldviscosities of the previous preparations after 4 hours and 24 hoursresting time.

1.3Stability with Lime

The viscosities of preparations containing 2% lime have been comparedwith the viscosities of the preparations without lime. 2 differentmethods have been used for the preparations with lime.

a) addition of lime before starch:

dispersion under mechanical stirring of 10 g lime in tap water in orderto have a total weight with starch of 510 g;

stirring at 450 rpm (6 holes-blade stirrer) for 5 minutes;

dispersion at 450 rpm of the starch and stirring at 450 rpm for 30minutes;

rest for 15 minutes;

measurement of the viscosity at 20° C. with a Brookfield viscometer RVTat 50, 20 and 10 rpm.

b) addition of lime after starch:

dispersion under mechanical stirring at 450 rpm (6 holes-blade stirrer)of the starch in tap water in order to have a total weight with lime of510 g;

stirring at 450 rpm for 30 minutes;

dispersion at 450 rpm of 10 g lime and stirring for 1 minute at 450 rpm;

rest for 15 minutes;

measurement of the viscosity at 20° C. with a Brookfield viscometer RVTat 50, 20 and 10 rpm.

In the 2 methods, the viscosities have been measured again after 24hours rest.

The tests with lime have been made on preparations having a Brookfieldviscosity at 20° C., 20 rpm of about 5000 mPa.s ±500 mPa.s

1.4Stability to Shear

The viscosities of the preparations submitted to 30 minutes of intenseshear at 1500 rpm have been compared to the viscosities of the samepreparations before shear:

dispersion under mechanical stirring at 450 rpm (6 holes-blade stirrer)of the starch in tap water with a few drops of an anti-foaming agent inorder to have a total weight of 500 g;

stirring at 450 rpm for 30 minutes;

rest for 15 minutes;

measurement of the viscosity at 20° C. with a Brookfield viscometer RVTat 50, 20 and 10 rpm;

stirring at 1500 rpm (6 holes-blade stirrer) for 30 minutes;

immediately after, measurement of the viscosity at 20° C. with aBrookfield viscometer RVT at 50, 20 and 10 rpm;

rest for 24 hours and measurement of the viscosity at 20° C. with aBrookfield viscometer RVT at 50, 20 and 10 rpm.

1.5Viscosities in a Formulation of Depilatory Paint

Formulation:

tap water: 270 g

lime (calcium hydroxide): 6 g

sodium sulphide 35%: 72 g

starch thickener: 4.5 or 6 g.

This corresponds to:

water: 100 g

lime: 2 g

sodium sulphide 60%: 14 g

starch thickener: 1.5 or 2 g.

The following method has been used for the preparation and viscositymeasurements:

dissolving of the sodium sulphide in the water;

dispersion of the lime under mechanical stirring and stirring for 5minutes;

dispersion of the starch at 450 rpm (4 blades propeller) and stirringfor 30 minutes;

rest for 15 minutes;

measurement of the viscosities at 20° C. with a Ford cup nr 4 and with aBrookfield viscometer RVT at 100, 50, 20 and 10 rpm.

2Results and Discussion

2.1Viscosities of Preparations in Tap Water

See Table 2.

A Brookfield viscosity at 20 rpm of about 5000 mPa.s±500 mpa-,s isobtained with:

product A at the concentration of 3.5%,

product B at the concentration of 7.5%,

product C at the concentration of 6.3%,

product O at the concentration of 10.0%,

product I at the concentration of 3.5%.

Product I based on amylopectin potato starch has a viscosity comparablewith the product A at the concentration of 3.5%. The preparations ofproduct I are fairly transparent and have a smooth and short texture,rather comparable with the preparations of product C. The speed ofswelling for product I is a little bit slower than for product C, but isfaster than for products A and B.

The products O and P have a comparable viscosity which is much lowerthan the viscosity of the 4 other products. They generate an importantamount of foam in case of stirring without anti-foaming agent. Theirpreparations have also a texture different from the other products, muchlonger which indicates that their effective degree of crosslinking islower than the degree of crosslinking of the other considered products.

2.2Stability to Ageing

See table 3.

The preparations in tap water are perfectly stable during at least 24hours for all the products.

2.3Stability with Lime

In the range of tests with lime, preparations of the products A and I at3.5%, product C at 6.3%, product O at 10%, which have without lime aboutthe same viscosity, have been compared. The 4 compared starches exhibitwith lime different behaviours (see—table 4).

For product I, the addition of lime causes an increase of the viscosity,probably due to better swelling in alkaline conditions. It isinteresting to remark that the increase of viscosity is about the samewhatever the addition of the lime is done before of after the additionof the starch. The viscosities obtained with lime are stable on ageingduring at least 24 hours. This indicates that the viscosity of alkalinepreparations is not dependent on the order of introduction of thereagents.

For product O, the increase of viscosity with lime is more importantthan for product I. The texture of the preparations has changed a lot bytaking a highly rubbery character, especially after 24 hours ageing.

The product C is the only product for which a strong decrease ofviscosity is observed with lime, probably due to its low hydroxypropylMS, in comparison with the other products.

2.4Stability to Shear

For the tests of stability to shear, again preparations of the productsA and I at 3.5%, C at 6.3%, and O at 10% have been compared (see table5).

The decrease of viscosity is more important for the products I and O(loss of about ½ of the initial viscosity) than for the products A and C(loss of about ⅓ of the initial viscosity). Most part of the initialviscosity is recovered after 24 hours rest. The resistance to shear ofthe 4 products can be judged satisfactory, considering the severity ofthe laboratory test. Under factory conditions, the shear stressesapplied during the preparation and the storage of the depilatory paintsare probably much lower.

2.5Viscosities in the Formulation of Depilatory Paint

See table 6.

Product I has in the depilatory paint a much higher thickening powerthan all the other products, at the concentration of 2%, whatever theshear rate of the viscosity measurement. At the concentration of 1.5%,the viscosity curves of the products I and C are comparable, apart fromthe measurement at 10 rpm which is a little bit higher for product C.

The 2 other products O and P, which have a low viscosity in tap water,exhibit also a low viscosity in the depilatory paint.

3Conclusion

The product I based on amylopectin potato starch has very goodthickening properties in tap water as well as in depilatory paint. Inaddition to that, it is easy to prepare and dissolves rather quickly,has a good behaviour with lime, and has a satisfactory resistance toshear. Consequently such a product presents a great interest for anapplication in depilatory paints.

Certain characteristics of the product I are different from the productsA and C. In comparison with the product A, the product I has:

a much higher viscosity in depilatory paint, especially at theconcentration of 2%,

a higher speed of swelling,

a better behaviour with lime.

In comparison with the product C, the product I has:

a much higher viscosity in depilatory paint,

a much higher viscosity in tap water and alkaline water,

a better resistance to lime.

The B products B, O and P based on potato starch have a much lowerthickening effect than the other products both in depilatory paint as intap water.

EXAMPLE 2

The example I has shown that the product I based on amylopectin potatostarch I has very good characteristics for an application as thickenerin depilatory paints for fellmongeries.

The crosslinking of the product I has been realized in suspension.Example 2 relates to samples of a comparable type of amylopectin potatostarch, but prepared according to the process of crosslinking insolution, and also to samples of a comparable type of starch based onwaxy-maize starch and crosslinked in suspension.

9 samples have been tested which can be classified in 3 ranges ofproducts:

4 samples based on amylopectin potato starch with a hydroxypropyl MS of0.6, crosslinked in solution with different amount ofepichlorohydrin(ECH),

3 samples based on amylopectin potato starch with a hydroxypropyl MS of0.2, crosslinked in solution with different amount of epichlorohydrin,

2 samples based on waxy-maize starch with a hydroxypropyl MS of 0.6,crosslinked in suspension with different amount of epichlorohydrin.

The viscosities of these 9 samples have been measured according tosimilar methods in the same formulation of depilatory paint. The resultshave been compared to the viscosities measured on the products I, A andC, previously discussed in example 1.

1Experiments

The same procedures as in example 1 have been used concerning themeasurements of viscosity in tap water and in the formulation ofdepilatory paint, the stability to ageing, with lime and to shear.

The speed of swelling of the different starches have been evaluated byrecording, with a Haake viscometer RV 12, curves of viscosity asfunction of the time (dispersion of the flakes in water in about 2seconds, time 0=end of the dispersion of the flakes in water, total timeof record: 15 min). Samples have been added at the concentration of 4%(2.40 g sample for 60 g tap water), apart from for the low viscousproducts, i.e. the products B at 7% and C at 6%.

For trials with water alkalinized with lime, 1.20 g lime (2%) has beendispersed in water prior to the addition of the starch.

2Results and Discussion

2.1Viscosities of Preparations in Tap Water

See table 7.

All 9 samples have a much higher viscosity than product C. At theconcentration of 5%, for the 3 ranges of samples, the viscosities areall higher when the degree of crosslinking is higher. It is the oppositeat the concentration of 2%: the viscosities appear lower when the degreeof crosslinking increases. This can be explained by an incompleteswelling of the product during the stirring time when the starchconcentration is low, and the concentration of swollen material is allthe lower as the degree of crosslinking increases.

For a same degree of crosslinking, the samples based on amylopectinpotato starch with a hydroxypropyl MS of 0.6 have a higher viscositythan the samples based on amylopectin potato starch with a hydroxypropylMS of 0.2. The 2 samples based on waxy-maize starch have also a lowerviscosity than the samples based on amylopectin potato starch with thesame hydroxypropyl MS of 0.6. A Brookfield viscosity at 20 rpm of about500 mPa.s±500 mpa.s is obtained at the concentration of:

3.3% for product E,

3.5% for products A and I,

3.6% for product G,

4.0% for products K, J and M,

5.0% for product D,

6.3% for product C.

The viscosity curves as function of the concentration are comparable forthe products E and I.

2.2—Stability to Ageing

See table 8.

In difference with product I, a slight loss of viscosity can be observedfor most of the new samples after 24 hours storage. This loss is all thehigher as the degree of crosslinking is lower, and is also higher forthe products having a hydroxypropyl MS of 0.2 instead of 0.6. Thedifference of viscosity after 24 hours storage is not significant forthe more crosslinked products based on amylopectin potato starch(products H, G and L), but is important for the less crosslinkedproducts (products D and J).

2.3—Speed of Swelling

See table 9.

In tap water, the speed of swelling is higher for the products based onamylopectin potato starch having a hydroxypropyl MS of 0.6, than for:

the products based on amylopectin potato starch having a hydroxypropylMS of 0.2,

the products based on waxy-maize,

the product A based on potato starch.

The products with the highest degree of crosslinking in each range ofsamples have a lower speed of swelling. The products E and I givecomparable curve of swelling.

Although its high degree of crosslinking, product B has a high speed ofswelling if prepared at high concentration (7%).

With water containing 2% lime, the samples based on amylopectin potatostarch having a hydroxypropyl MS of 0.6 have a higher viscosity than intap water, especially those having the highest degree of crosslinking.The speeds of swelling are not very different from the speed of swellingin tap water. The products E and I give again comparable curve ofswelling. For products based on amylopectin potato starch having ahydroxypropyl MS of 0.2, the end-viscosities are much lower than in tapwater, and the speeds of swelling are still low.

The product A exhibits a very low speed of swelling in alkaline water.After 15 min stirring, its swelling is far to be complete.

The product C swells very fast, but the end-viscosity is much lower thanin tap water. The low end-viscosity in water alkalinized with lime is aconsequence of its low hydroxypropyl MS.

2.4Viscosities in the Formulation of Depilatory Paint

See:

tables 10 and 11 for viscosities of depilatory paints containing 2.0%starch,

table 12 for viscosities of depilatory paints containing 1.5% starch.

For the range of samples based on amylopectin potato starch with MS 0.6,the highest viscosities are obtained for the product E having anintermediary degree of crosslinking (% ECH: 0.025). The more crosslinkedproduct (product H—% ECH: 0.10) gives the lowest viscosities. The 2other samples (product G—% ECH: 0.05 and product D—% ECH: 0.0125) havean intermediary thickening power. The curve of viscosity of the productE at the concentration of 2.0% is very close to the curve of the productI. At the concentration of 1.5%, the product E gives even higherviscosities than the product I.

For the range of samples based on amylopectin potato starch with MS 0.2,the viscosities are all the highest as the degree of crosslinking islower. As for the previous range of amylopectin potato starch samples,the more viscous product has been produced with 0.025% ECH (product J).At the concentration of 2.0%, the products with MS 0.6 are more viscousthan products with MS 0.2 for a same degree of crosslinking. At theconcentration of 1.5%, the product J has a slightly lower viscosity thanthe product E when measured at a high shear rate (100 and 50 rpm), butis characterised by a higher viscosity when measured at a low shear rate(10 rpm). The best products of the range of samples based on amylopectinpotato starch with MS 0.2 have a better thickening power than theproducts A, B and C based on potato starch.

The 2 waxy-maize based products have lower viscosities than theamylopectin potato starch based products. The product M, which is theless crosslinked, is the more viscous of these 2 products.

A decrease of viscosity is observed on the depilatory paints duringstorage, with certain samples based on amylopectin potato starch and MS0.6, especially at the concentration of 2% and for measurements at lowshear rate (10 and 20 rpm). This decrease is of the order of 10% for themeasurements at 20 rpm, the most part occurs during the first 4 hoursstorage. This is not observed with the samples based on amylopectinpotato starch and MS 0.2, for which a small increase of viscosity ratheroccurs. An explanation could be that for products with MS 0.6 and at theconcentration of 2%, the first measurement after preparation correspondsto a state at/or near the peak of swelling. At a lower concentration,e.g. 1.5%, there is no peak during the swelling, and consequently themeasurements of viscosity after preparation and after 4 hours are close.The products with MS 0.2 need a longer time for a complete swelling, andhave no viscosity peak at the 2 considered concentrations (see alsotable 9).

On the whole, each of the 3 ranges of products, and especially theranges of products based on amylopectin potato starch, contains productswhich enable to obtain high viscosities in depilatory paint. Its curveof viscosity at the concentration of 2.0% is very close to the curve ofthe product I. At the concentration of 1.5%, E gives even higherviscosities than I.

2.5Stability with Lime

Certain samples (those which have given the best results in depilatorypaints for each range of products) have been prepared with 2% lime atthe following or concentration:

product E (amylopectin potato starch—MS 0.6): 3.3%

product J (amylopectin potato starch—MS 0.2): 4.0%

product M (waxy-maize starch—MS 0.6): 4.0%.

These concentrations enable to reach in tap water about the same levelof viscosity (see table 13). The table 9 has also to be taken intoaccount.

A different behaviour is observed between the samples with a MS of 0.6and the products with a MS of 0.2.

The products with MS of 0.6 give in the presence of lime slightlyincreased viscosities, not very dependent of the order of introductionof the lime. Only the viscosities after 24 hours of storage when lime isadded after the swelling of the starch are significantly higher.

For the product J, the swelling is strongly inhibited when lime is addedbefore starch, and in any case the viscosity after 24 hours of storageare very low. This behaviour is also different from the behaviour of theproduct C, for which the viscosities are much lower with lime than intap water.

It must also be noted that the behaviour of certain of the consideredproducts in water with 2% lime is rather different to the behaviour inthe depilatory paint which contains in addition sodium sulphide; e.g.the products C and J give very low viscosities in water with lime, butrelatively high viscosities in the depilatory paint. The product E giveshigh viscosities in water with lime as well as in depilatory paints.

2.6Stability to Shear

The tests of stability to shear have been done on the same samples andat the same concentration than tests with lime (see table 14).

As previously mentioned for product I, a higher decrease of viscosity isobserved for the products E and J than for the products A and C. Theproduct M based on waxy-maize starch has given intermediary results. Therecovery of viscosity is low after 24 hours rest for the product J whichhas a low hydroxypropyl MS.

It must be recalled that this test is probably much more severe than theshear stresses applied during the preparation and the storage of thedepilatory paints.

3Conclusion

The products based on amylopectin potato starch, especially those havinga hydroxypropyl MS of 0.6 such as the product E, have good thickeningproperties for the depilatory paints. The characteristics of the productE are very close to the characteristics of the product I.

The products based on amylopectin potato starch, especially the productsE and I, have as main advantages in front of the products A and C basedon potato starch, of a higher viscosity in depilatory paint and a lowersensitivity to lime. They have also in front of the product A theadvantages of a much higher speed of swelling.

High visosities in depilatory paint can also be obtained with theproducts based on amylopectin potato starch with a MS of 0.2, such asthe products J and K. The best products of this range of samples have abetter thickening power than the products A and C based on common potatostarch.

The samples based on waxy-maize starch have lower viscosities and aslightly lower speed of swelling than the best products based onamylopectin potato starch with a MS of 0.6. Their thickening power indepilatory paints is nevertheless comparable and in certain conditionshigher than the products based on common potato starch.

EXAMPLE 3

Pregelatinized hydroxypropylated crosslinked starch based on amylopectinpotato starch, especially the products E and G, have very goodcharacteristics for an application as thickener in depilatory paints forfellmongeries.

Another sample (product F) based on amylopectin potato starch has beenprepared according to the same process of production (crosslinking insolution) as the products E and G. The new sample has the samehydroxypropyl MS (0.6), but has an intermediary degree of crosslinking(0.033% epichlorohydrin instead of 0.025% for E and 0.050% for G).

The characteristics of the product F (viscosities in tap water and in adepilatory paint, speed of swelling, characteristics of stability) havebeen measured according to similar methods as in example 2 and comparedto the characteristics of the products E and G.

1Experiments

The test procedures are identical to the procedures described in example2.

The measurements of viscosity in tap water and in the depilatory paint,and the stabilities to ageing have been made again on the products E andG, in order to check the repeatability of the results. The figuresmentioned in the tables of this report are averages of the new resultsand the results previously indicated in example 2.

A test of swelling in water containing lime and sodium sulphide has beenadded to the tests of swelling in tap water and in water alkalinizedwith 2% lime, according to the same procedure (recorded with a Haakeviscometer RV 12). The amounts of water (50.6 g), lime (1,2 g) andsodium sulphide 35% (14,4 g) have been calculated in order to have thesame ratios than in the formulation of the depilatory paint, e.g.: 100%water−2% lime−14% sodium sulphide 60%. The amount of starch added is 2,4g (4%). This percentage is much higher than in the depilatory paints,but is necessary for being in the range of viscosities which can bedetected by the Haake viscometer. The order of introduction of thereagent is:

1. water

2. solubilization of the sodium sulphide;

3. dispersion of the lime, stirring during 2 minutes;

4. addition of the starch, start of the record of the swelling curve,(total time of record: 15 min).

2Results and Discussion

2.1Viscosities of Preparations in Tap Water

See table 15.

A Brookfield viscosity at 20° C. and 20 rpm of about 5000 mpa.s±500mpa.s is obtained at the concentration of:

3.4% for product E,

3.5% for products F and A,

3.6% for product G.

The 3 products based on amylopectin potato starch and also the product Ahave about the same viscosity at the concentration of it 4.0%. Below4.0%, the less crosslinked product (product E) has the highest viscosityand the more crosslinked product (product G) the lowest viscosity. It isthe opposite at the concentration of 5.0%, the viscosity increases whenthe degree of crosslinking increases.

The new measurements of viscosity on the products E and G are notsignificantly different from the measurements mentioned in example 2.

2.2Stability to Ageing

See table 16.

At very low concentration (2.0%), the viscosities after 24 hours restare much higher than after preparation. To the difference of thepreparations at higher concentration, not completely swollen particlescan be observed in the preparations at 2%. The low concentrations, forwhich the viscosity reached after 30 minutes stirring is very low andnot sufficient for suspending the not completely swollen material, needin fact a longer time of stirring.

At the intermediary concentrations (3.0-4.0%), a slight increase of theviscosity after 24 hours is generally observed.

At the concentration of 5.0%, there is a loss of viscosity after 24hours rest which is all the lower as the degree of crosslinking ishigher. For the 2 more crosslinked products (F and G), the difference ofviscosity after 24 hours is very low.

2.3Viscosities in the Formulation of Depilatory Saint

See table 17.

The product F has significantly the highest viscosity when added at theconcentration of 1.5%, and is very close to the less crosslinked product(product E) at the concentration of 2.0%. These 2 samples are the mostviscous products (with product I—see examples 1 and 2) in depilatorypaint amongst all the considered products. The more crosslinked product(product G) has a lower thickening power than the 2 other samples basedon amylopectin potato starch.

The decrease of viscosity during storage is in fact low for these 3products. The new measurements of viscosity on samples E and G are notsignificantly different from the measurements mentioned in example 2.

2.4Speed of Swelling

See table 18.

The speed of swelling in the 3 mediums (tap water, water alkalinizedwith 2% lime, water containing 2% lime and 14% sodium sulphide) of the 3samples based on amylopectin potato starch have been compared to thecurves of swelling of the products A, B and C.

The behaviours of these products are very different as function of thekind of water.

For the 3 samples based on amylopectin potato starch, the speed ofswelling is close in tap water and in water alkalinized with lime, butthe viscosity is higher with lime. The speed of swelling is a little bithigher in the presence of sodium sulphide. The highest speed of swellingwith sodium sulphide is observed for F. The final viscosity is lowerwith sodium sulphide than with only lime for the less crosslinkedproduct (product E), identical for the intermediary crosslinked product(product F), higher for the more crosslinked product (product G).

The property of for example product F to give very close viscosities inwater containing only 2% lime and in water containing 2% lime+14% sodiumsulphide is very interesting for an application in depilatory paints,because that means that the product will have the same behaviourwhatever the percentage of sodium sulphide in the depilatory paint.

The product A needs a longer time for swelling than the 3 previousproducts, whatever the kind of water. The addition of 2% lime decreasesthe speed of swelling and the viscosity. The presence of the sodiumsulphide in the alkaline water has a beneficial effect concerning thespeed of swelling and the viscosity. But the final viscosity with limeand sodium sulphide is much lower than the 3 previous samples.

The product B has another type of behaviour. The speed of swelling ismuch faster in alkaline medium than in tap water, and viscosities aremuch higher. But the addition of sodium sulphide has an unfavourableeffect on viscosity. The viscosities reached with the product B are muchlower than with the 3 samples based on amylopectin potato starch.

The product C has also a behaviour different to all the other products.The swelling is very fast whatever the type of water. The presence ofsodium sulphide provokes a strong increase of the viscosity incomparison with tap water or water with only lime.

2.5Stability with Lime

See table 19.

For the 2 more crosslinked products (products F and G), the addition oflime provokes a significant increase of the viscosity. The increase ofviscosity is about the same when the addition of lime is done before orafter the starch. The obtained viscosities are stable to ageing duringat least 24 hours. This indicates that for these 2 products, theviscosity of the alkaline preparation is not very dependent on the orderof addition of the reagents.

For the less crosslinked product (product E), the increase of viscosityin the presence of lime is lower, especially when lime is added beforestarch. A significantly higher viscosity is observed after 24 hoursstorage when lime is added after the swelling of the starch.Consequently the viscosity in the presence of lime is for the product Emore dependent on the order of addition of the reagents than the 2previous products.

2.6Stability to Shear

See table 20.

The decrease of viscosity is lower for the more crosslinked products(products F and G) than for the product E. The results of the test ofshear are about the same for the products F and G. The resistance toshear of these products can be judged satisfactory considering theseverity of the laboratory test.

3Conclusion

The products based on amylopectin potato starch have good properties foran application in depilatory paints. They are characterised by:

a high thickening power in depilatory paint, high viscosities can beobtained even at low concentration (1.5%), especially with the productsE and F;

a fast speed of swelling in the presence of lime and sodium sulphide;

a viscosity not very dependent on the percentage of sodium sulphide,especially for the product F;

a satisfactory stability to shear;

a good stability to ageing.

These products can advantageously replace in this application theproducts based on common starch, such as product A due mainly to theirhigher viscosity in depilatory paint and their much higher speed ofswelling, and such as product C which has a lower thickening effect indepilatory paint and a higher sensitivity to lime.

EXAMPLE 4

This example illustrates the use of a thickener of the present inventionfor the dehairing of hide or skin, according to a quick-pull system. Insuch a system, the pulling of the hairs from the skin can start no morethan 2 hours after the paint has been sprayed on the skin. Typicaldepilation paints for quick-pull systems are characterized by thepresence of sodium hydroxide and a high amount of sodium sulphide intheir formulation.

The product A based on potato starch and the product F based onamylopectin potato starch have been tested in the following formulation:

water: 100 g

sodium hydroxide 2.3 g

lime (calcium hydroxide): 3 g

sodium sulphide 60%: 35 g

starch thickener: 2.2 g for A and 1.5 g for F.

The viscosities obtained with the products A and F after preparation areindicated in table 21. As already seen in the example 3, the product Fhas a higher thickening power than the product A. The same viscosity canbe obtained at the concentration of 1.5% for the product F and at theconcentration of 2.2% for the product A. The stability of the viscosityduring time of the depilation paint with the product F is satisfactory.Only a small increase of viscosity is noted: from an initial viscosityof 270 mpa.s (at 20 rpm), the viscosity increase to 302 mPa.s after 4hours storage and to 320 mPa.s after 24 hours storage.

EXAMPLE 5

This example illustrates the use of a thickener of the present inventionfor the dehairing of hide or skin, according to a long-pull system. Inlong-pull systems, the paint has a more gentle action of dehairing thanin quick-pull systems, which decreases the risks of damage of the skins.Consequently the time of action of the paint must be longer (e.g. 5hours) before starting the pulling of the hairs from the skin. Generallysodium hydroxide is not used in the formulation of the paints forlong-pull systems.

Different products based on potato starch, amylopectin potato starch,and waxy-maize starch have been tested in the following formulation:

tap water: 100 g

lime (calcium hydroxide): 4 g

sodium sulphide 60%: 14 g

starch thickener: 1.5 g or 2.0 g.

For an easy dehairing, it is important to have a good migration of thepaint through the skin, the paint being sprayed on what was the fleshside of the skin. This characteristic has been appraised by the help ofa test of migration. The principle of the test is to measure the weightof paint which has been absorbed by a filter-paper after migrationthrough a piece of leather during a given time. the procedure of thetest is the following:

sticking of a disc of leather on a metallic ring;

placing of the ring on a weighed standardized paper-filter (disc ofleather in contact with the paper-filter);

pouring in the ring of 30 g depilation paint prepared according to theprevious formulation;

weighing of the paper-filter after a time of contact with the disc ofleather of 15-30 and 60 minutes;

calculation of the weight of liquid absorbed by the paper-filter after15-30 and 60 minutes.

The speed of migration through the disc of leather is all the faster asthe weight of liquid absorbed by the paper-filter after 15 minutes ishigher.

The viscosities and the weight of liquid absorbed by the paper-filterare indicated for the different products tested according thisformulation, in table 22.

A much higher viscosity can be reached with the products based onamylopectin potato starch, than with the other types of starch. Theproducts H—L and Q, all based on amylopectin potato starch, have at theconcentration of 1.5% a viscosity equal or higher to the viscosity atthe concentration at 2.0% of the more viscous product of the samplesbased on potato starch (product C).

Certain products based on amylopectin potato starch combine a highthickening power with a high speed of migration through a leather skin.This is especially the case of the product Q, which despite the highviscosity of its preparation at the concentration of 1.5%, enables toprepare a depilation paint with a high speed of migration, comparablewith the speed of migration measured on preparations (at theconcentration of 2.0%) of the best samples based on potato starch.

TABLE 1 List of the products considered in the examples ECH Hydroxy- MSProduct Starch Crosslinking^(a) % propylation^(a) (HP) A PS solution0.02 solution 0.7 B PS suspension 0.08 solution 0.8 C PS suspension0.025 suspension 0.14 D APS solution 0.0125 solution 0.6 E APS solution0.025 solution 0.6 F APS solution 0.033 solution 0.6 G APS solution0.050 solution 0.6 H APS solution 0.100 solution 0.6 I APS suspension0.010 solution 0.6 J APS solution 0.025 solution 0.2 K APS solution0.033 solution 0.2 L APS solution 0.050 solution 0.2 M WMS suspension0.02 solution 0.6 N WMS suspension 0.03 solution 0.6 O PS solution0.0188 solution 0.66 P PS solution 0.0188 solution 0.75 Q APS solution0.192 solution 0.2 ^(a)Method of derivatizing PS = potato starch APS =amylopectin potato starch WMS = waxy maize starch

TABLE 2 Brookfield vicosities (mPa.s) at 20° C. of preparations in tapwater as function of the concentration. Concentration 2.0% 3.0% 3.5%4.0% 5.0% 6.0% 6.3% 7.0% 7.5% 8.0% 10.0% Product A 10 rpm 470 3040 696015880 37200 20 rpm 390 2320 4670 10320 23250 50 rpm 290 1470 3000 564012300 Product B 10 rpm 80 3140 5880 13000 42000 20 rpm 83 2550 4600 945026000 50 rpm 84 1750 3050 5740 14120 Product C 10 rpm 24 2960 5200 752021100 30000 20 rpm 10 2200 3730 5260 14100 20500 50 rpm 18 1480 24303360 8520 11900 Product O 10 rpm 1220 11860 2820 41000 4200 6280 20 rpm920 8870 2120 25750 3100 4740 50 rpm 640 4680 1440 14420 2100 3220Product P 10 rpm 1130 20 rpm 870 50 rpm 610 Product I 10 rpm 260 792011200 16500 20 rpm 200 5060 7160 10650 50 rpm 134 2860 4020 6050

TABLE 3 Stability to ageing of the preparations in tap water -Brookfield viscosities (mPa · s) at 20° C. Product A B C O IConcentration 3.5% 10.0% 6.3% 10.0% 3.5% Viscosity after: preparation 10rpm 6960 42000 7520 6280 7920 20 rpm 4670 26000 5260 4740 5060 50 rpm3000 14120 3360 3220 2860 24 hours 10 rpm 7060 58000 7820 5650 7960 20rpm 4620 37600 5440 4340 5080 50 rpm 2980 19800 3420 2930 2860

TABLE 4 Effect of lime on the Brookfield viscosities (mPa · s) at 20° C.Product A C O I Concentration 3.5% 6.3% 10.0% 3.5% Viscosity withoutlime 10 rpm 6960 7520 6280 7920 20 rpm 4670 5260 4740 5060 50 rpm 30003360 3220 2860 with 2% lime added before starch, measurement afterpreparation 10 rpm 3260 1430 17300 18700 20 rpm 2080 1010 11650 11000 50rpm 1150 670 7140 5700 measurement after 24 hours 10 rpm 4400 2420 2050017000 20 rpm 2880 1720 13500 9880 50 rpm 1640 990 8200 4880 with 2% limeadded after starch, measurement after preparation 10 rpm 12600 760 2250014200 20 rpm 8460 550 14650 8600 50 rpm 5130 327 8520 4420 measurementafter 24 hours 10 rpm 10520 880 30500 15000 20 rpm 7240 616 19350 862050 rpm 4900 362 11200 4260

TABLE 5 Effect of shear on the Brookfield viscosities (mPa · s) at 20°C. Product A C O I Concentration 3.5% 6.3% 10.0% 3.5% Viscosity after:preparation 10 rpm 6960 7520 6280 7920 20 rpm 4670 5260 4740 5060 50 rpm3000 3360 3220 2860 30 mn shear at 1500 rpm 10 rpm 4620 4940 3360 370020 rpm 3450 3550 2580 2460 50 rpm 2220 2320 1800 1500 after 30 mn shearand 24 h rest 10 rpm 6900 5920 4680 6500 20 rpm 4640 4230 3680 4120 50rpm 3040 2720 2560 2400 Ratio: vis. after shear/ initial viscosity 10rpm 0.66 0.66 0.54 0.47 20 rpm 0.74 0.67 0.55 0.49 50 rpm 0.74 0.69 0.580.52 Ratio: vis. after shear and rest/ initial viscosity 10 rpm 0.990.79 0.75 0.82 20 rpm 0.99 0.80 0.78 0.82 50 rpm 1.01 0.81 0.80 0.84

TABLE 6 Ford cup 4 and Brookfield viscosities (mPa.s) of depilationpaints (20° C.). Product A B C O P I Concentration 1.5% 2.0% 2.4% 1.5%2.0% 2.0% 2.0% 1.5% 2.0% pH 12.9 12.9 12.9 12.9 12.9 12.9 12.9 12.9 12.9Measurements after preparation Ford cup 4 (s) 11.6 13.3 11.9 11.7 13.115.0 14.7 11.8 19.0 Brookfield  10 rpm 99 308 284 190 390 177 143 160828  20 rpm 75 197 157 116 234 145 123 107 580  50 rpm 60 117 70 67 125123 105 73 364 100 rpm 51 93 55 58 92 112 98 67 258 Measurements after 4hours Ford cup 4 (s) 11.6 13.3 11.2 11.7 13.1 14.7 14.3 11.6 18.3Brookfield  10 rpm 92 304 77 190 367 145 144 147 812  20 rpm 70 195 58118 227 122 122 99 560  50 rpm 58 117 46 68 127 103 104 69 348 100 rpm51 93 41 55 93 100 100 64 250 Measurements after 24 hours Ford cup 4 (s)11.7 13.4 11.1 11.7 13.4 14.7 14.2 11.6 19.0 Brookfield  10 rpm 95 30867 193 384 133 140 145 800  20 rpm 73 202 54 120 250 113 118 100 558  50rpm 60 122 44 69 140 97 101 70 352 100 rpm 51 94 39 57 108 93 97 64 252

TABLE 7 Brookfield vicosities (mPa.s) at 20° C. of preparations in tapwater as function of the concentration. Concentration 2.0% 3.0% 3.3%3.5% 3.6% 4.0% 5.0% 6.0% 6.3% Product A PS 10 rpm 470 3040 6960 1588037200 MS 0.7 20 rpm 390 2320 4670 6960 23250 50 rpm 290 1470 3000 467012300 Product I APS 10 rpm 260 7920 11200 16500 MS 0.6 20 rpm 200 50607160 10650 50 rpm 134 2860 4020 6050 Product H APS 10 rpm 25800 MS 0.620 rpm 16100 50 rpm 8720 Product G APS 10 rpm 138 2610 6400 7920 25000MS 0.6 20 rpm 114 1705 4160 5120 15550 50 rpm 89 1050 2360 2880 8400Product E APS 10 rpm 312 7080 9400 15800 MS 0.6 20 rpm 220 4560 600010500 50 rpm 148 2550 3360 5620 Product D APS 10 rpm 640 8000 MS 0.6 20rpm 430 5360 50 rpm 258 3220 Product L APS 10 rpm 18000 MS 0.2 20 rpm11400 50 rpm 6260 Product K APS 10 rpm 156 7820 13880 MS 0.2 20 rpm 1204990 8840 50 rpm 84 2820 4980 Product J APS 10 rpm 191 4500 7840 12960MS 0.2 20 rpm 137 2870 5000 8360 50 rpm 97 1650 2840 4740 Product N WMS10 rpm 13760 MS 0.6 20 rpm 8580 50 rpm 4740 Product M WMS 10 rpm 1257240 12400 MS 0.6 20 rpm 109 4600 7820 50 rpm 79 2580 4340

TABLE 8 Stability to ageing of the preparations in tap water -Brookfield viscosities at 20°C. and 20 rpm. Viscosity Viscosity after 24Hydroxy Concen- after hours propyl tration preparation ageing ProductBase MS % ECH (%) (mPa.s) (mPa.s) A PS 0.7 0.02 3.5 4670 4620 I APS 0.60.01 3.5 5060 5080 H APS 0.6 o.1 S.o 16100 15800 F APS 0.6 0.05 3.6 51204940 E APS 0.6 0.025 3.3 4560 4100 D APS 0.6 0.0125 5.0 5360 2920 L APS0.2 0.05 5.0 11400 10520 K APS 0.2 0.033 4.0 4990 3850 J APS 0.2 0.0254.0 5000 3110 N WMS 0.6 0.03 5.0 B5BO 7500 M WMS 0.6 0.02 4.0 4600 4870

TABLE 9 Swelling in tap water and in water alkalinized with 2% lime.Swelling Medium Vis- Hydroxy and Peak cosity propyl concen- Peak vis-after Product Base MS % ECH tration time cosity 15 min A PS 0.7 0.02 TW4% ≧15′ — 142 AW 4% ≧15′ — 42 B PS 0.8 0.08 TW 7% ≧15′ — 71 AW 7% nm nmnm AW 4% 0′45″ 30 19 C PS 0.14 0.025 TW 6% 4′ 89 82 AW 6% 1′55″ 42 29 IAPS 0.6 0.010 TW 4% 4′15″ 129 97 AW 4% 4′50″ 172 131 H APS 0.6 0.100 TW4% 8′ 61 60 AW 4% 7′30″ 135 127 G APS 0.6 0.050 TW 4% 4′25″ 108 93 AW 4%4′30″ 160 136 E APS 0.6 0.025 TW 4% 4′45″ 136 92 AW 4% 5′00″ 160 115 DAPS 0.6 0.0125 TW 4% 3′35″ 141 76 AW 4% 3′45″ 123 86 L APS 0.2 0.050 TW4% 15′ 51 51 AW 4% 10′ 25 24 K APS 0.2 0.033 TW 4% 8′ 79 72 AW 4% 12′ 2726 J APS 0.2 0.025 TW 4% 10′50″ 78 74 AW 4% 14′ 45 44 N WMS 0.6 0.03 TW4% 15′ 45 44 AW 4% 6′ 86 78 M WMS 0.6 0.02 TW 4% 9′ 62 58 AW 4% 6′10 9682 TW = tap water AW = water alkalinized with 2% lime nm = notmeasurable

TABLE 10 Ford cup 4 and Brookfield viscosities of depilation paints(mPa.s) at 20° C. containing 2.0% starch, for amylopectin potato starchbased products with a hydroxyropyl MS of 0.6 Product A C I H G E DCharacteristics base PS PS APS APS APS APS APS MS 0.7 0.14 0.6 0.6 0.60.6 0.6 % ECH 0.02 0.025 0.010 0.1 0.05 0.025 0.0125 Measurements afterpreparation Ford cup 4 (s) 13.3 13.1 19.0 14.8 16.1 20.2 18.8 Brookfield 10 rpm 308 390 828 392 448 720 508  20 rpm 197 234 580 268 315 514 372 50 rpm 117 125 364 170 205 334 254 100 rpm 93 92 258 132 160 246 197Measurements after 4 hours Ford cup 4 (s) 13.3 13.1 18.3 14.5 15.9 20.518.5 Brookfield  10 rpm 304 367 812 348 374 650 475  20 rpm 195 227 560240 284 478 356  50 rpm 117 127 348 168 197 320 248 100 rpm 93 93 250130 156 240 194 Measurements after 24 hours Ford cup 4 (s) 13.4 13.419.0 14.9 15.9 20.2 18.0 Brookfield  10 rpm 308 384 800 326 362 630 440 20 rpm 202 250 558 236 276 472 336  50 rpm 122 140 352 164 196 320 236100 rpm 94 108 252 128 157 236 186

TABLE 11 Ford cup 4 and Brookfield viscosities of depilation paints(mPa.s) at 20° C. containing 2.0% starch, for amylopectin potato starchbased products with a hydroxypropyl MS of 0.2, and for waxy-maize starchbased products with a hydroxypropyl MS of 0.6. Product A C I L K J N MCharacteristics base PS PS APS APS APS APS WMS WMS MS 0.7 0.14 0.6 0.20.2 0.2 0.6 0.6 % ECH 0.02 0.025 0.010 0.05 0.033 0.025 0.03 0.02Measurements after preparation Ford cup 4 (s) 13.3 13.1 19.0 14.9 15.716.1 14.2 15.2 Brookfield  10 rpm 308 390 828 280 324 396 172 260  20rpm 197 234 580 204 248 290 140 198  50 rpm 117 125 364 144 178 198 119146 100 rpm 93 92 258 121 145 154 106 126 Measurements after 4 hoursFord cup 4 (s) 13.3 13.1 18.3 14.6 15.7 16.1 13.8 14.7 Brookfield  10rpm 304 367 812 320 332 432 172 228  20 rpm 195 227 560 224 250 310 140176  50 rpm 117 127 348 148 178 203 116 136 100 rpm 93 93 250 121 144159 104 120 Measurements after 24 hours Ford cup 4 (s) 13.4 13.4 19.014.8 15.7 16.1 13.8 14.9 Brookfield  10 rpm 308 384 800 320 324 404 160232  20 rpm 202 250 558 224 244 300 124 180  50 rpm 122 140 352 153 174201 114 138 100 rpm 94 108 252 124 143 158 105 121

TABLE 12 Ford cup 4 and Brookfield Viscosities of depilation paints(mPa.s) at 20° C. containing 1.5% starch. Product A C I G E D K J MCharacteristics base PS PS APS APS APS APS APS APS WMS MS 0.7 0.14 0.60.6 0.6 0.6 0.2 0.2 0.6 % ECH 0.02 0.025 0.01 0.05 0.025 0.0125 0.0330.025 0.02 Measurements after preparation Ford cup 4 (s) 11.6 11.7 11.812.8 13.2 13.2 12.5 12.5 12.0 Brookfield  10 rpm 99 190 160 174 218 145123 245 118  20 rpm 75 116 107 125 158 119 92 152 86  50 rpm 60 67 73 86112 96 76 101 68 100 rpm 51 58 67 81 100 89 73 88 63 Measurements after4 hours Ford cup 4 (s) 11.6 11.7 11.6 12.6 13.2 13.2 12.5 12.5 12.0Brookfield  10 rpm 92 190 147 152 196 153 130 240 116  20 rpm 70 118 99112 144 125 100 152 85  50 rpm 58 68 69 82 105 99 78 97 67 100 rpm 51 5564 78 95 92 73 84 63 Measurements after 24 hours Ford cup 4 (s) 11.711.7 11.6 12.6 13.2 13.2 12.7 12.6 12.0 Brookfield  10 rpm 95 193 145144 202 152 132 244 115  20 rpm 73 120 100 109 154 122 98 161 85  50 rpm60 69 70 81 117 98 77 110 68 100 rpm 51 57 64 77 103 90 72 96 64

TABLE 13 Effect of lime on the Brookfield viscosities (mPa.s) at 20° C.and 20 rpm. Product A C I E J M Characteristics base PS PS APS APS APSWMS MS 0.7 0.14 0.6 0.6 0.2 0.6 % ECH 0.02 0.025 0.010 0.025 0.025 0.02Concentration 3.5% 6.3% 3.5% 3.3% 4.0% 4.0% Viscosity without 4670 52605060 4560 5000 4600 lime Viscosity with 2% lime added before starch -measurement after: 2080 1010 11000 5310 1130 6400 preparation 24 hoursrest 2880 1720 9880 5750 210 7340 Viscosity with 2% lime added afterstarch - measurement after: 8460 550 8600 7000 6560 6240 preparation 24hours rest 7240 616 8620 9300 454 9940

TABLE 14 Effect of shear on the Brookfield viscosities (mPa.s) at 20° C.and 20 rpm. Product A C I E J M Characteristics base — — AP AP AP WM MS— — 0.6 0.6 0.2 0.6 % ECH — — — 0.025 0.025 0.02 Concentration 3.5% 6.3%3.5% 3.3% 4.0% 4.0% Viscosity before shear 4670 5260 5060 4560 5000 4600Viscosity after 30 mn 3450 3550 2460 2020 1870 2400 shear at 1500 rpmViscosity after 30 mn 4640 4230 4120 2720 2030 3640 shear and 24 hoursrest Ratio viscosity after 0.74 0.67 0.55 0.44 0.37 0.52 shear/initialviscosity Ratio viscosity after 0.99 0.80 0.78 0.60 0.41 0.79 shear andrest/initial viscosity

TABLE 15 Brookfield vicosities (mPa · s) at 20° C.) of preparations intap water as function of the concentration. Concentration Product AProduct E Product F Product G 2.0% 10 rpm 470 312 300 138 20 rpm 390 220220 114 50 rpm 290 148 148 89 3.0% 10 rpm 3040 3600 3430 2550 20 rpm2320 2420 2280 1680 50 rpm 1470 1430 1330 1050 3.3% 10 rpm 6930 20 rpm4500 50 rpm 2430 3.5% 10 rpm 6960 8740 7920 6400 20 rpm 4670 5700 50004160 50 rpm 3000 3240 2800 2360 3.6% 10 rpm 7800 20 rpm 5070 50 rpm 28504.0% 10 rpm 15880 10780 11560 10480 20 rpm 6960 6900 7220 6720 50 rpm4670 3850 4000 3740 5.0% 10 rpm 37200 15960 19800 24500 20 rpm 2325010600 12400 15280 50 rpm 12300 5670 6760 8280

TABLE 16 Stability to ageing of the preparations in tap water -Brookfield viscosities (mPa · s) at 20° C. and 20 rpm. Product E ProductF Product G Concentration (0.025% ECH) (0.033% ECH) (0.050% ECH) 2.0%after prep. 220 220 114 after 24 h 400 354 284 3.0% after prep. 24202280 1680 after 24 h 2720 2480 2060 4.0% after prep. 6900 7220 6720after 24 h 6460 7500 7060 5.0% after prep. 10600 12400 15280 after 24 h8300 11450 14420

TABLE 17 Ford cup 4 and Brookfield viscosities of depilation paints(mPa.s) at 20° C. Comparison with products A and C. Product A C E F GConcentration 1.5% 2.0% 1.5% 2.0% 1.5% 2.0% 1.5% 2.0% 1.5% 2.0%Measurements after preparation Ford cup 4 (s) 11.6 13.3 11.7 13.1 13.320.5 13.4 20.1 12.8 16.3 Brookfield  10 rpm 99 308 190 390 224 728 306668 179 453  20 rpm 75 197 116 234 161 517 204 476 127 318  50 rpm 60117 67 125 114 334 132 315 87 207 100 rpm 51 93 58 92 101 246 108 232 81162 Measurements after 4 hours Ford cup 4 (s) 11.6 13.3 11.7 13.1 13.320.0 13.5 19.4 12.6 16.1 Brookfield  10 rpm 92 304 190 367 202 657 274626 161 393  20 rpm 70 195 118 227 148 481 190 456 116 294  50 rpm 58117 68 127 107 322 123 308 85 201 100 rpm 51 93 55 93 96 241 102 227 80159 Measurements after 24 hours Ford cup 4 (s) 11.7 13.4 11.7 13.4 13.320.0 13.6 19.5 12.6 16.2 Brookfield  10 rpm 95 308 193 384 200 639 264616 155 382  20 rpm 73 202 120 250 151 474 186 450 113 286  50 rpm 60122 69 140 112 321 119 308 84 199 100 rpm 51 94 57 108 100 237 101 22679 158

TABLE 18 Swelling in tap water, in water alkalinized with 2% lime, andin water containing 2% lime + 14% sodium sulphide. Swelling Concen- PeakPeak Viscosity after Product Medium tration time viscosity 15 min A TW4% ≧15′ — 152  AW 4% ≧15′ — 42 SW 4% ≧15′ — 62 B TW 7% ≧15′ — 71 AW 7%nm nm nm AW 4% 0′45″  30 19 SW 4% ≧15′ — 11 C TW 6% 4  89 82 AW 6% 1′55″ 42 29 SW 6% nm nm nm SW 4% 3′00″  71 58 E TW 4% 4′55″ 136 92 AW 4%5′00″ 160 115  SW 4% 5′20″ 109 95 F TW 4% 4′15″ 115 91 AW 4% 3′30″ 163125  SW 4% 3′00″ 154 125  G TW 4% 4′25″ 108 93 AW 4% 4′30″ 160 136  SW4% 3′40″ 187 153  TW = tap water AW = water alkalinized with 2% lime SW= water containing 2% lime and 14% sodium sulphide nm = not measurable

TABLE 19 Effect of lime on the Brookfield viscosities (mPa · s) at 20°C. and 20 rpm. Product A E F G Concentration 3.5% 3.3% 3.5% 3.6%Viscosity without lime 4670 4560 5000 5120 Viscosity with 2% lime addedbefore starch - measurement after: preparation 2080 5310 8140 10260 24hours rest 2880 5750 8960 11000 Viscosity with 2% lime added afterstarch - measurement after: preparation 8460 7000 9040 10560 24 hoursrest 7240 9300 9940 11200

TABLE 20 Effect of shear on the Brookfield viscosities (mPa · s) at 20°C. and 20 rpm. Product A E F G Concentration 3.5% 3.3% 3.5% 3.6%Viscosity before shear 4670 4560 5000 5120 Viscosity after 30 mn shear3450 2020 3000 3160 at 1500 rpm Viscosity after 30 mn shear 4640 27204060 4180 and 24 hours rest Ratio viscosity after shear/ 0.74 0.44 0.600.62 initial viscosity Ratio viscosity after shear 0.99 0.60 0.81 0.82and rest/initial viscosity

TABLE 21 Ford cup 4 and Brookfield viscosities at 20° C. in a depilationpaint for quick-pull system. Product A F Concentration 2.2% 1.5% pH 12.612.6 Measurements after preparation 14.1 14.0 Ford cup 4 (second)Brookfield (mPa · s)  10 rpm 420 448  20 rpm 262 270  50 rpm 146 148 100rpm 107 108

TABLE 22 Viscosities at 20° C. and speed of migration in a depilationpaint for long-pull system. Product A B C H L Q N Characteristics basePS PS PS PS PS PS PS MS 0.7 0.8 0.14 0.6 0.2 0.2 0.6 % ECH 0.02 0.080.025 0.10 0.05 0.19 0.03 Concentration 2.0 2.0 2.0 1.5 1.5 1.5 2.0 (%)Viscosity Ford cup 4 13.5 11.2 13.7 13.8 12.9 13.6 14.8 (second)Brookield (mpa.s)  10 rpm 432 23 660 708 672 828 312  20 rpm 270 24 400422 388 494 224  50 rpm 148 25 208 222 192 246 147 100 rpm 101 27 135141 111 151 122 Migration test (*) -weight of absorbed liquid (g) after:15 mn — 15.4 13.3 — 5.2 14.4 — 30 mn 0.1 — 16.0 5.2 7.0 — 0.1 60 mn 0.3— — 7.8 8.6 — 0.4 (*): the maximum capacity of liquid absorption of theused paper-filter is about 17-18 g.

What is claimed is:
 1. A depilatory paint thickener comprising a starchderived from a starch comprising from 95 to 100% amylopectin molecules.2. A depilatory paint thickener according to claim 1 wherein said starchis obtained from tubers or roots, which are genetically modified so thatsaid starch contains essentially only amylopectin molecules.
 3. Adepilatory paint thickener according to claim 1 wherein said starch isderived from a plant, which is genetically modified so that said starchcontains essentially only amylopectin molecules.
 4. A depilatory paintthickener according to claim 3 wherein said plant is a potato.
 5. Adepilatory paint thickener according to claim 1 wherein said starch is across-linked starch.
 6. A depilatory paint thickener according to claim1 wherein said starch is a stabilised starch.
 7. A depilatory paintthickener according to claim 1 wherein said starch is an instant starch.8. A depilatory paint comprising a thickener according to claim
 1. 9. Amethod for depilating an animal hide or skin comprising treating saidhide or skin with a depilatory paint according to claim
 8. 10. Adepilated hide or skin produced by a method according to claim
 9. 11. Aleather or leather product comprising a depilated hide or skin accordingto claim
 10. 12. A wool comprising a hide or skin treated by a methodaccording to claim
 9. 13. A depilatory paint thickener according toclaim 1 wherein said starch is an epichlorohydrin cross-linked starch.14. A depilatory paint thickener according to claim 1 wherein saidstarch is a hydroxylated starch.